package 模拟实现二叉树;

import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {

    public static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode node1 = new TreeNode('A');
        TreeNode node2 = new TreeNode('B');
        TreeNode node3 = new TreeNode('C');
        TreeNode node4 = new TreeNode('D');
        TreeNode node5 = new TreeNode('E');
        TreeNode node6 = new TreeNode('F');
        TreeNode node7 = new TreeNode('G');
        TreeNode root = node1;
        root.left = node2;
        root.right = node3;
        node2.left = node4;
        node3.left = node5;
        node3.right = node6;
        node5.right = node7;
        return root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size2(TreeNode root) {
        if (root == null){
            return;
        }
        nodeSize ++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size(TreeNode root) {
        if(root == null){
            return 0;
        }
        return size(root.left) + size(root.right) +1;
    }

    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root.left == null && root.right == null){
            leafSize++;
            return;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount(TreeNode root) {
        if (root == null){
            return 0;
        }
        if (root.left == null && root.right == null){
            return 1;
        }
        return getLeafNodeCount(root.left) + getLeafNodeCount(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root == null){
            return 0;
        }
        if (k == 1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)
                + getKLevelNodeCount(root.right,k-1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null){
            return 0;
        }
        int Lhight = getHeight(root.left);
        int Rhight = getHeight(root.right);
       return Lhight > Rhight ?Lhight + 1:Rhight + 1;
    }

    // 检测值为value的元素是否存在,并返回该结点的地址
    TreeNode find(TreeNode root, char val) {
        if (root == null){
            return null;
        }
        if (root.val == val){
            return root;
        }
        TreeNode ret1 = find(root.left,val);
        if(ret1 != null){
            return ret1;
        }
        TreeNode ret2 = find(root.right,val);
        if(ret2 != null){
            return ret2;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null){
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()){
            TreeNode cur = queue.poll();
            System.out.print(cur.val + " ");
            if (cur.left != null){
                queue.offer(cur.left);
            }
            if (cur.right != null){
                queue.offer(cur.right);
            }
        }
    }

    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null){
            return true;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()){
            TreeNode cur = queue.poll();
            if (cur == null){
                break;
            }
            queue.offer(cur.left);
            queue.offer(cur.right);
        }
        while (!queue.isEmpty()){
            if (queue.poll() != null){
                return false;
            }
        }
        return true;
    }
}